The present invention relates to an automobile vehicle seat including a backrest pivoting in relation to the seat pan and which can be placed in a position typically called the “table” position where the rear of the backrest is more or less horizontal.
Current vehicle seats, whether they are placed at the front, in intermediary position (when there are three rows of seats), or at the rear, increasingly include a “table” function for the backrests. This function can be independent of the backrest tilt angle setting function or combined with it. The table function can also exist without provision for a backrest tilt comfort setting function.
Moreover, seats, especially the front seats, can include a backrest forward tilt functionality, that is a partial folding of the backrest onto the seat pan to allow, for example, easier access to the seats located behind the said seat.
In seats combining the table and backrest tilt angle setting functionalities, it is known, for example, to add to a conventional discontinuous-type setting mechanism, also called “discontinuous hinge”, a possibility of placing the backrest in the “table” position and to maintain it in this position by using a conventional discontinuous hinge notching system. In solutions of this type, the pivoting of the backrest for the table function is done around the same axis as the pivoting for the tilt setting or “comfort” setting which requires that this pivoting axis be located sufficiently high to allow the backrest to be folded down onto the seat pan until the rear of the backrest is horizontal.
As such a configuration is not always suitable for technology or ergonomic reasons, it has already been proposed to achieve the pivotings required respectively for comfort and for the table function on different axes. The “comfort” setting of the backrest is then achieved around a first axis, generally located fairly low down, by means of a conventional fine adjustment mechanism such as the above-mentioned discontinuous hinge; and the pivoting of the backrest for the table function is ensured around a second axis located higher by a simpler mechanism as its aim is only to ensure the pivoting between the two utilisation positions: current and “table”, and the locking in each of these two positions without the need for fine adjustment.
Such an arrangement especially offers the advantage of facilitating the placing of the backrest in table position, with the rear wall of the backrest positioned horizontally. Indeed, the said second axis can then be placed sufficiently high in relation to the seat pan so that the thickness of the seat pan cushions and the padding of the backrest do not limit the folding down of the backrest onto the seat pan.
A disadvantage is that the hinge enabling the table function, even if it is simplified, necessarily creates an increase in size at a relatively high level on the sides of the backrest and this can be incompatible with the arrangement on these sides of elements which must be placed fairly low down such as, for example, certain inflatable airbags, integrated into the sides of the backrest.
Also, such an arrangement complicates the layout and the making of elements ensuring the link between the seat pan and the backrest which must provide two offset pivoting axes with the respective locking means.
Document DE-10123776 shows a system in which the seat pan is installed on links forming, with the seat pan and a base attached to the floor, a deformable parallelogram allowing the seat pan to be moved forwards and downwards by deformation of this parallelogram. Also, the backrest is hinged in relation to this base by means of another complex link system arranged to move the backrest both upwards and pivot it forwards so that it can be folded down onto the seat pan moved forward. The combination of moving the seat pan forwards and moving the backrest hinge upwards allows the backrest to be folded down with its rear face more or less horizontal. This device is however complex due to the fact that two link systems are required for the respective movements of the seat pan and the backrest.
Document JP-2002/248980 shows another system which tends to solve the problem mentioned above, with a single axis for the pivoting of the backrest in relation to the seat pan, this axis being located in a low position and overcoming the problems limiting the folding down of the backrest due to the overall size of the seat cushions and paddings. This system, to allow the rear of the backrest to be placed in horizontal position, when the seat pan cushion limits the pivoting of the backrest, allows the seat pan itself to pivot around an axis located towards the front of the seat pan which allows the rear of the seat pan to be raised and therefore the seat pan to be placed in a tilted position thus allowing the rear wall of the backrest to be placed in a horizontal position. In other words, the insufficient movement authorised at the level of the hinge between the backrest and the seat pan is compensated for by the pivoting of the seat pan itself with respect to the vehicle floor. The rear of the seat pan is maintained in raised position by a torque link-configured system, maintained in deployed position by a spring, for the table function of the backrest, and maintained in the folded position, for current use of the seat, by a lock.
This system allows therefore the backrest to be placed in horizontal position, the modification of the tilt angle of the seat pan providing the additional pivoting angle required. This system does not allow the seat pan to be maintained in a position other than the two extreme positions mentioned above. Furthermore, the height of the front of the seat pan is conditioned by the pivoting axis of the seat pan. It therefore cannot be used to ensure a seat pan tilt angle adjustment for example to ensure better comfort for the user.